山美水库氮营养盐滞留特征及其影响因素的多时间尺度分析

水库对氮营养盐的滞留效应对水体富营养化防控有重要影响,为揭示不同时间尺度下水库氮营养盐的滞留特征及影响因素的差异,通过构建山美水库流域生态动力学模型,在统计水库氮滞留量和滞留率的基础上,从年、月、日不同时间尺度对氮营养盐的滞留效应进行分析;并通过多元线性相关分析,对入库流量、出入库流量比、水力滞留时间、流速、温度5种因素的影响进行研究.结果表明: 不同时间尺度下山美水库的氮滞留过程均呈现波动特征.在年尺度上,水库主要呈现正滞留效应,是流域重要的氮汇;在月尺度上,氮滞留呈现丰枯期变化特征,水库在源和汇的角色上发生转变;在日尺度上,枯水年氮滞留过程波动剧烈,滞留率在-300%～100%之间变化.不同时间尺度下,出入库流量比、流速因子均是影响水库氮滞留的重要因素;随着时间尺度的降低,入库流量和温度因子对氮滞留的影响程度有所增强;水力滞留时间对氮滞留的影响程度则随时间尺度变化而有正负差异.

Multiple time-scale analysis of nitrogen retention characteristics and influencing factors in Shanmei Reservoir,Fujian, China.

The retention effect of reservoir on nitrogen is an important influence factor on the eutrophication prevention and control. In order to reveal the differences of nitrogen retention characteristics and the influence factors at multiple timescales, an ecological dynamic model was developed in Shanmei Reservoir watershed. Based on the retention flux and retention rate calculation, the nitrogen retention effect was analyzed at three time scales of yearly, monthly and daily, respectively. Furthermore, multiple linear correlation analysis was conducted to analyze the influence of inflow runoff, ratio of inflow to outflow, residence time, velocity and temperature on the retention of nitrogen in the reservoir. The results showed that the process of nitrogen retention always displayed fluctuant characteristic at different time scales. On a yearly scale, the reservoir mainly played a role of nitrogen sink; on a monthly scale, seasonal variation of nitrogen retention and release effect made the reservoir as nitrogen sink in wet period and as nitrogen source in dry period; on a daily scale, the nitrogen retention process fluctuated intensely, with the retention rate ranging from -300% to 100% in dry year. At different time scales, ratio of inflow to outflow and velocity were always the important factors to affect nitrogen retention in the reservoir, with significant correlation coefficients consistently. With the time scale changing from yearly to monthly, daily, the influence degree of inflow runoff and temperature on nitrogen retention was gradually strengthened. The correlations between the residence time and retention rate could be positive or negative at different time scales.